Refrigeration cycle apparatus

ABSTRACT

A refrigeration cycle apparatus includes: a compressor in a first refrigerant path between a first heat exchanger and a second heat exchanger; a first flow rate adjustment device in a second refrigerant path between the first heat exchanger and the second heat exchanger; a refrigerant storage device provided in a third refrigerant path between the first heat exchanger and the second heat exchanger, connected in parallel with a part of the second refrigerant path, and configured to store refrigerant flowing from the second refrigerant path; a second flow rate adjustment device provided in the third refrigerant path, and configured to adjust a flow rate of refrigerant between the refrigerant storage device and the second refrigerant path; and a controller configured to control the second flow rate adjustment device to block flow of refrigerant from the second refrigerant path into the refrigerant storage device when cooling operation is started.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of International Patent Application No. PCT/JP2021/000098 filed on Jan. 5, 2021, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a refrigeration cycle apparatus.

BACKGROUND

A refrigeration cycle apparatus uses more refrigerant for cooling operation than for heating operation. Some conventional refrigeration cycle apparatuses are therefore equipped with a refrigerant storage device that temporarily stores redundant refrigerant in a refrigerant circuit during heating operation.

There has been a conventional refrigeration cycle equipped with a refrigerant storage device as disclosed for example in WO2016/121068 (PTL 1) that includes: a refrigerant circuit including a compressor, a flow path switching device, a heat source-side heat exchanger, a first expansion device, and a use-side heat exchanger; and a liquid backflow suppression circuit connected in parallel with the first expansion device and including a second expansion device, an on-off valve, and a high-pressure receiver connected between the second expansion device and the on-off valve.

PATENT LITERATURE

-   PTL 1: WO2016/121068 (FIG. 1)

When the conventional refrigeration cycle apparatus starts cooling operation under the condition that the outdoor air temperature is extremely low, the outdoor air temperature causes the temperature of the refrigerant storage device to be extremely lower than the temperature of water with which heat is to be exchanged at the use-side heat exchanger. Thus, at the start of such cooling operation, there is a possibility that the pressure difference between the pressure in the refrigerant storage device and a refrigerant path to which the use-side heat exchanger is connected causes refrigerant to flow from the refrigerant path into the refrigerant storage device and to be stored therein. After the start of such cooling operation, due to a relatively large heat capacity of the refrigerant storage device that hinders increase of the temperature of the refrigerant storage device, for example, there is a possibility that refrigerant stored in the refrigerant storage device cannot be discharged. Thus, when cooling operation is performed while refrigerant is stored in the refrigerant storage device, shortage of the amount of refrigerant required for cooling operation results in deterioration of the capacity of the refrigeration cycle apparatus.

SUMMARY

An object of a refrigeration cycle apparatus of the present disclosure is to prevent deterioration of the capacity of the refrigeration cycle apparatus during cooling operation.

The present disclosure relates to a refrigeration cycle apparatus. The refrigeration cycle apparatus includes: a compressor provided in a first refrigerant path located between a first heat exchanger and a second heat exchanger; a first flow rate adjustment device provided in a second refrigerant path located between the first heat exchanger and the second heat exchanger; a refrigerant storage device provided in a third refrigerant path located between the first heat exchanger and the second heat exchanger, the third refrigerant path being connected in parallel with a part of the second refrigerant path, the refrigerant storage device being configured to store refrigerant flowing from the second refrigerant path; a second flow rate adjustment device provided in the third refrigerant path, and configured to adjust a flow rate of refrigerant between the refrigerant storage device and the second refrigerant path; and a controller configured to control the second flow rate adjustment device to block flow of refrigerant from the second refrigerant path into the refrigerant storage device when cooling operation is started.

In the refrigeration cycle apparatus of the present disclosure, the second flow rate adjustment device is controlled, when cooling operation is started, to block flow of refrigerant from the second refrigerant path into the refrigerant storage device, and therefore, when cooling operation is started under the condition that the outdoor air temperature is extremely low, refrigerant can be prevented from flowing into the refrigerant storage device. Thus, in the refrigeration cycle of the present disclosure, there is no shortage of the amount of refrigerant for cooling operation, and deterioration of the function of the refrigeration cycle apparatus can be avoided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a refrigerant circuit configuration of a refrigeration cycle apparatus 1 according to Embodiment 1.

FIG. 2 shows the refrigerant circuit configuration of refrigeration cycle apparatus 1 according to Embodiment 1.

FIG. 3 is a flowchart for a CPU 102 of a controller 100 to control a second flow rate adjustment device 18 and a third flow rate adjustment device 19 when cooling operation is started, according to Embodiment 1.

FIG. 4 shows a refrigerant circuit configuration of a refrigeration cycle apparatus 1A according to Embodiment 2.

FIG. 5 shows the refrigerant circuit configuration of refrigeration cycle apparatus 1A according to Embodiment 2.

FIG. 6 is a flowchart of control for CPU 102 of controller 100 to perform defrosting operation during heating operation, according to Embodiment 2.

FIG. 7 is a flowchart of control for CPU 102 of controller 100 to perform defrosting operation during heating operation, according to Embodiment 3.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described in detail hereinafter with reference to the drawings. In the following, a plurality of embodiments are described, and it is intended originally that features described in connection with the embodiments are combined appropriately. In the drawings, the same or corresponding parts are denoted by the same reference characters, and a description thereof is not herein repeated.

Embodiment 1

FIGS. 1 and 2 show a refrigerant circuit configuration of a refrigeration cycle apparatus 1 according to Embodiment 1. FIG. 1 shows a state of a refrigerant circuit in refrigeration cycle apparatus 1 during cooling operation. FIG. 2 shows a state of the refrigerant circuit in refrigeration cycle apparatus 1 during heating operation.

Referring to FIGS. 1 and 2 , refrigeration cycle apparatus 1 includes the refrigerant circuit, and the refrigerant circuit includes a compressor 13, a flow path switching device 15, a first heat exchanger 11, a second heat exchanger 12, a first flow rate adjustment device 14, a refrigerant storage device 16, a first check valve 21, a second check valve 22, a third check valve 17, a second flow rate adjustment device 18, and a third flow rate adjustment device 19. The refrigerant circuit is a passage for refrigerant used in refrigeration cycle apparatus 1. In FIGS. 1 and 2 , the direction in which refrigerant flows is indicated by arrows.

Refrigeration cycle apparatus 1 includes, as a refrigerant path, a first refrigerant path F1, a second refrigerant path F2, a third refrigerant path F3, a fourth refrigerant path F4, and a fifth refrigerant path F5.

First heat exchanger 11 is an air heat exchanger that causes heat to be exchanged between outdoor air and refrigerant. First heat exchanger 11 functions as a condenser for refrigerant during cooling operation, and functions as an evaporator for refrigerant during heating operation. A blower fan (not shown) is provided in the vicinity of first heat exchanger 11 for blowing air toward first heat exchanger 11. The blower fan has a function of sucking in outdoor air and discharging, to the outside, air of which heat has been exchanged with refrigerant by first heat exchanger 11.

Second heat exchanger 12 is a water heat exchanger that causes heat to be exchanged between water of an indoor unit (not shown) and refrigerant. Second heat exchanger 12 functions as an evaporator for refrigerant during cooling operation, and functions as a condenser for refrigerant during heating operation.

In first refrigerant path F1 between first heat exchanger 11 and second heat exchanger 12, compressor 13 that compresses refrigerant is provided. Compressor 13 is driven by a motor controlled by an inverter, for example.

In second refrigerant path F2 between first heat exchanger 11 and second heat exchanger 12, first flow rate adjustment device 14 is provided. First flow rate adjustment device 14 has a function of reducing the pressure of refrigerant to expand the refrigerant, and is configured in the form of an electronic expansion valve capable of adjusting the flow rate, for example. First flow rate adjustment device 14 is capable of adjusting the flow rate of refrigerant in second refrigerant path F2 during both cooling operation and heating operation, and is used for reducing the pressure of refrigerant to expand the refrigerant.

In third refrigerant path F3 connected in parallel with a part of second refrigerant path F2, refrigerant storage device 16 is provided that is capable of storing refrigerant flowing therein from second refrigerant path F2. Specifically, refrigerant storage device 16 is located between first flow rate adjustment device 14 and second heat exchanger 12 and connected in parallel with second refrigerant path F2. Refrigerant storage device 16 is a metal cylindrical refrigerant tank and capable of storing refrigerant.

In third refrigerant path F3, third check valve 17 is provided that is capable of causing refrigerant to flow from the inside of refrigerant storage device 16 in only the one direction to second refrigerant path F2 between refrigerant storage device 16 and first flow rate adjustment device 14. When the pressure in refrigerant storage device 16 becomes higher, by a reference value or more, than the pressure of second refrigerant path F2 between first flow rate adjustment device 14 and second heat exchanger 12, third check valve 17 causes refrigerant in refrigerant storage device 16 to be discharged to second refrigerant path F2.

In third refrigerant path F3, second flow rate adjustment device 18 capable of opening/closing the refrigerant path between refrigerant storage device 16, and first flow rate adjustment device 14 and second heat exchanger 12, is provided. Second flow rate adjustment device 18 is configured in the form of a valve capable of adjusting the flow rate, like an electronic expansion valve, for example, and is set in either one of the full-open state and the full-close state. As second flow rate adjustment device 18, an electromagnetic valve to be set in either one of the full-open state and the full-close state may also be used. Second flow rate adjustment device 18 may also be controlled to have an opening other than the full-open state and the full-close state.

The refrigerant circuit of refrigeration cycle apparatus 1 uses more refrigerant during cooling operation than during heating operation. During cooling operation as shown in FIG. 1 , basically all the refrigerant in the refrigerant circuit is used in the refrigerant circuit, and therefore, it is not necessary to store refrigerant in refrigerant storage device 16. In contrast, during heating operation as shown in FIG. 2 , basically, if all the refrigerant in the refrigerant circuit is used in the refrigerant circuit, the amount of refrigerant is excessive and therefore, it is necessary to store redundant storage refrigerant 30 in refrigerant storage device 16 as schematically shown in FIG. 2 .

In fourth refrigerant path F4 located between second refrigerant path F2 and the suction side of compressor 13, third flow rate adjustment device 19 is provided that supplies refrigerant in liquid state (hereinafter referred to as liquid refrigerant) to compressor 13. Third flow rate adjustment device 19 is provided for supplying liquid refrigerant to the suction side of compressor 13, with the purpose of preventing compressor 13 from being superheated even when refrigerant that is likely to be increased in temperature, like R32 refrigerant for example, is used. Specifically, a part of liquid refrigerant flowing in second refrigerant path F2 is supplied to compressor 13 through third flow rate adjustment device 19. Third flow rate adjustment device 19 is configured in the form of a valve capable of adjusting the flow rate, like an electronic expansion valve, for example.

Fourth refrigerant path F4 includes a first branch path F41, a second branch path F42, and a supply path F43. First branch path F41 is a passage for allowing a part of liquid refrigerant to flow from second refrigerant path F2 to third flow rate adjustment device 19 during cooling operation in FIG. 1 . Second branch path F42 is a passage for allowing a part of liquid refrigerant to flow from second refrigerant path F2 to third flow rate adjustment device 19 during heating operation in FIG. 2 .

First branch path F41 branches off from second refrigerant path F2 located between first heat exchanger 11 and first flow rate adjustment device 14, and is connected to the inlet side of third flow rate adjustment device 19. Second branch path F42 branches off from second refrigerant path F2 located between second heat exchanger 12 and first flow rate adjustment device 14, and is connected to the inlet side of third flow rate adjustment device 19. Supply path F43 connects first branch path F41 or second branch path F42 through the outlet side of third flow rate adjustment device 19 to the suction side of compressor 13.

In first branch path F41, first check valve 21 is provided that causes liquid refrigerant to flow in only the one direction from first heat exchanger 11 to third flow rate adjustment device 19 during cooling operation. In second branch path F42, second check valve 22 is provided that causes liquid refrigerant to flow in only the one direction from second heat exchanger 12 to third flow rate adjustment device 19 during heating operation. Each of first check valve 21 and second check valve 22 causes liquid refrigerant to flow toward third flow rate adjustment device 19, in response to the fact that the pressure on the inlet side becomes higher, by a reference value or more, than the pressure on the outlet side.

During cooling operation, liquid refrigerant flows in second refrigerant path F2 between first heat exchanger 11 and first flow rate adjustment device 14. Thus, during cooling operation, as shown in FIG. 1 , liquid refrigerant flows from first branch path F41 through first check valve 21 to third flow rate adjustment device 19 and further flows from supply path F43 through third flow rate adjustment device 19 to the suction side of compressor 13. During heating operation, liquid refrigerant flows in second refrigerant path F2 between second heat exchanger 12 and first flow rate adjustment device 14. Thus, during heating operation, as shown in FIG. 2 , liquid refrigerant flows from second branch path F42 through second check valve 22 to third flow rate adjustment device 19 and further flows from supply path F43 through third flow rate adjustment device 19 to the suction side of compressor 13.

In first refrigerant path F1, the path on the discharge side of compressor 13 is connected to either one of first heat exchanger 11 and second heat exchanger 12 through flow path switching device 15. Flow path switching device 15 switches the flow path in which refrigerant flows, and is configured in the form of a four-way valve, for example.

For cooling operation, as shown in FIG. 1 , flow path switching device 15 switches the refrigerant flow path to connect the path on the discharge side of compressor 13 to first heat exchanger 11. For heating operation, as shown in FIG. 2 , flow path switching device 15 switches the refrigerant flow path to connect the path on the discharge side of compressor 13 to second heat exchanger 12.

Refrigerant that can be used in refrigeration cycle apparatus 1 includes a single refrigerant, a pseudo-azeotropic refrigerant mixture, a zeotropic refrigerant mixture, and the like.

Controller 100 includes a CPU (Central Processing Unit) 102, a memory 104 (ROM (Read Only Memory) and RAM (Random Access Memory)), and an input/output buffer (not shown) for input and output of various signals, for example. In the controller, various electronic components are mounted on a control circuit board. The control circuit board includes a plurality of input ports used for input of signals such as detection signals of various sensors, for example, and a plurality of output ports used for output of signals necessary for control of an actuator, such as control signals for first flow rate adjustment device 14, second flow rate adjustment device 18, and third flow rate adjustment device 19, for example.

CPU 102 deploys and executes, on the RAM for example, programs stored in the ROM. The programs stored in the ROM are each a program in which a process procedure for controller 100 is defined. In accordance with these programs, controller 100 controls each device in refrigeration cycle apparatus 1. This control is not limited to processing by software, but may also be processing by dedicated hardware (electronic circuit).

Refrigeration cycle apparatus 1 is provided with various sensors. Sensors like those as described below are provided, for example. The discharge side of compressor 13 is provided with a discharge temperature sensor 51 that detects temperature T1 of refrigerant discharged from compressor 13 (this temperature is hereinafter referred to as discharge temperature). First heat exchanger 11 is provided with a heat exchanger temperature sensor that detects the temperature of first heat exchanger 11. The heat exchanger temperature sensor detects the temperature of frost adhering to first heat exchanger 11. The inlet side of second heat exchanger 12 is provided with an inlet temperature sensor that detects the temperature of refrigerant. The outlet side of second heat exchanger 12 is provided with an outlet temperature sensor that detects the temperature of refrigerant. Detection signals of various sensors including a detection signal of discharge temperature sensor 51 that represents discharge temperature T1 of compressor 13, as illustrated as an exemplary one, are input to controller 100.

Controller 100 provides a control signal to each of compressor 13, first flow rate adjustment device 14, flow path switching device 15, second flow rate adjustment device 18, and third flow rate adjustment device 19. Controller 100 controls the operating frequency of compressor 13 based on the control signal. Controller 100 controls the opening of first flow rate adjustment device 14 based on the control signal. Controller 100 controls flow path switching device 15 to switch the flow path based on the control signal. Controller 100 controls the opening of second flow rate adjustment device 18 based on the control signal. Controller 100 controls the opening of third flow rate adjustment device 19 based on the control signal.

Next, FIGS. 1 and 2 are used to describe operations of refrigeration cycle apparatus 1.

Referring to FIG. 1 , an operation of refrigeration cycle apparatus 1 during cooling operation is described. For cooling operation, controller 100 controls flow path switching device 15 such that the flow path in flow path switching device 15 as shown in FIG. 1 is established. Controller 100 controls the opening of first flow rate adjustment device 14 based on superheat. For example, controller 100 determines the opening of first flow rate adjustment device 14, such that the suction-side superheat of compressor 13 determined from respective temperatures detected by an inlet temperature sensor and an outlet temperature sensor of first heat exchanger 11 is equal to a target value (3° C. to 5° C., for example), and controls the opening of first flow rate adjustment device 14.

High-temperature high-pressure gas refrigerant generated through compression and discharged by compressor 13 flows in first refrigerant path F1 through flow path switching device 15 and enters first heat exchanger 11. The high-temperature high-pressure refrigerant entering first heat exchanger 11 discharges heat into outdoor air or the like, and is accordingly condensed into high-pressure liquid refrigerant. In second refrigerant path F2, the high-pressure liquid refrigerant discharged from first heat exchanger 11 enters first flow rate adjustment device 14 where the liquid refrigerant is expanded to have a reduced pressure and become low-temperature low-pressure gas-liquid two-phase refrigerant. In second refrigerant path F2, the gas-liquid two-phase refrigerant discharged from first flow rate adjustment device 14 enters second heat exchanger 12. The gas-liquid two-phase refrigerant entering second heat exchanger 12 exchanges heat with water to become low-temperature low-pressure gas refrigerant. The gas refrigerant discharged from second heat exchanger 12 flows through flow path switching device 15 to be sucked into compressor 13 where the gas refrigerant is compressed again.

During cooling operation, all the refrigerant in the refrigerant circuit is used in the refrigerant circuit, and therefore, it is not necessary to store refrigerant in refrigerant storage device 16. When cooling operation is started under the condition that the outdoor air temperature is extremely low, however, the outdoor air temperature causes the temperature of refrigerant storage device 16 to be extremely lower than the temperature of water with which heat is to be exchanged at second heat exchanger 12. Accordingly, depending on the pressure difference between the pressure in refrigerant storage device 16 and the pressure in second refrigerant path F2, there is a possibility that refrigerant in second refrigerant path F2 flows from the downstream side of first flow rate adjustment device 14 into refrigerant storage device 16.

Further, if refrigerant entering refrigerant storage device 16 is stored therein at the start of cooling operation under the condition that the outdoor air temperature is extremely low, a relatively large heat capacity of refrigerant storage device 16 hinders increase of the temperature of refrigerant storage device 16 and hinders increase of the pressure in refrigerant storage device 16, even when refrigerant flows in the refrigerant circuit after cooling operation is started. Therefore, if refrigerant is stored in refrigerant storage device 16 at the start of cooling operation, refrigerant is not discharged from refrigerant storage device 16 even after the start of cooling operation due to the pressure difference between the pressure in refrigerant storage device 16 and the pressure in second refrigerant path F2 that is higher than the pressure in refrigerant storage device 16.

If refrigerant is thus stored in refrigerant storage device 16 during cooling operation, shortage of the amount of refrigerant required for cooling operation results in deterioration of the capacity of refrigeration cycle apparatus 1. In view of this, when cooling operation is started, controller 100 controls second flow rate adjustment device 18 to set its opening in the full-close state and controls second flow rate adjustment device 18 to keep its opening in the full-close state during operation after the start of cooling operation. Accordingly, shortage of the amount of refrigerant during cooling operation is avoided, and thus deterioration of the capacity of refrigeration cycle apparatus 1 can be avoided.

During cooling operation, liquid refrigerant flows in second refrigerant path F2 between first heat exchanger 11 and first flow rate adjustment device 14. Thus, during cooling operation, liquid refrigerant flows from first branch path F41 through first check valve 21 to third flow rate adjustment device 19, and further flows through third flow rate adjustment device 19 into supply path F43 and to the suction side of compressor 13. In this way, even when refrigerant that is likely to be increased in temperature, like R32 refrigerant for example, is used, compressor 13 can be prevented from being superheated.

Referring to FIG. 2 , an operation during heating operation is described. For heating operation, controller 100 controls flow path switching device 15 such that the flow path in flow path switching device 15 as shown in FIG. 2 is established. Controller 100 controls the opening of first flow rate adjustment device 14 based on the degree of subcooling. Specifically, controller 100 determines the opening of first flow rate adjustment device 14, such that the degree of subcooling at the outlet of second heat exchanger 12 determined from respective temperatures detected by the inlet temperature sensor and the outlet temperature sensor of second heat exchanger 12 is equal to a target value (3° C. to 5° C., for example).

High-temperature high-pressure gas refrigerant generated through compression and discharged by compressor 13 flows in first refrigerant path F1 through flow path switching device 15 and enters second heat exchanger 12. The high-temperature high-pressure refrigerant entering second heat exchanger 12 discharges heat into water to be condensed into high-pressure liquid refrigerant. In second refrigerant path F2, the high-pressure liquid refrigerant discharged from second heat exchanger 12 enters first flow rate adjustment device 14 where the liquid refrigerant is expanded to have a reduced pressure and become low-temperature low-pressure gas-liquid two-phase refrigerant. In second refrigerant path F2, the gas-liquid two-phase refrigerant discharged from first flow rate adjustment device 14 enters first heat exchanger 11. At this time, second flow rate adjustment device 18 is controlled to be an open state by controller 100. Thus, residual refrigerant is stored in refrigerant storage device 16. The gas-liquid two-phase refrigerant entering first heat exchanger 11 exchanges heat with outdoor air to become low-temperature low-pressure gas refrigerant. The gas refrigerant discharged from first heat exchanger 11 flows through flow path switching device 15 to be sucked into compressor 13 where the gas refrigerant is compressed again.

During heating operation, the amount of refrigerant used for heating is smaller than that used for cooling during cooling operation, and therefore, it is necessary to store residual refrigerant in refrigerant storage device 16. Therefore, controller 100 controls second flow rate adjustment device 18 to set its opening in the full-open state during heating operation. In this way, the amount of refrigerant can be prevented from becoming excessive during heating operation.

During heating operation, liquid refrigerant flows in second refrigerant path F2 between second heat exchanger 12 and first flow rate adjustment device 14. Thus, during heating operation, liquid refrigerant flows from second branch path F42 through second check valve 22 to third flow rate adjustment device 19, and further flows from supply path F43 through third flow rate adjustment device 19 to the suction side of compressor 13. In this way, even when refrigerant that is likely to be increased in temperature, like R32 refrigerant for example, is used, compressor 13 can be prevented from being superheated.

When first heat exchanger 11 is frosted during the above-described heating operation, refrigeration cycle apparatus 1 performs defrosting operation for melting frost on first heat exchanger 11. Specifically, when controller 100 determines that a defrosting operation start condition for first heat exchanger 11 is satisfied during heating operation, controller 100 performs cooling operation by switching flow path switching device 15 to the path for cooling operation and causing first heat exchanger 11 to function as a condenser. For example, when the temperature detected by the heat exchanger temperature sensor provided at first heat exchanger 11 is lower than a reference temperature (0° C., for example), controller 100 determines that first heat exchanger 11 is frosted and the defrosting operation start condition is satisfied.

FIG. 3 is a flowchart for CPU 102 of controller 100 to control second flow rate adjustment device 18 and third flow rate adjustment device 19 when cooling operation is started, according to Embodiment 1.

In step S1, controller 100 starts cooling operation. In step S2, controller 100 sets second flow rate adjustment device 18 in the full-close state that is capable of blocking refrigerant from flowing into refrigerant storage device 16, when cooling operation is started.

In step S3, controller 100 determines whether or not discharge temperature T1 of compressor 13 detected by discharge temperature sensor 51 is higher than a threshold value. For the threshold value in this case, an upper limit is set, such as 100° C., for example, at which compressor 13 is not recognized as a superheated state.

When controller 100 determines in step S3 that discharge temperature T1 is lower than or equal to the threshold value, controller 100 controls, in step S4, third flow rate adjustment device 19 to be set in the close state, transitions to a normal control state for cooling operation, and makes a return. In contrast, when controller 100 determines in step S3 that discharge temperature T1 is higher than the threshold value, controller 100 controls, in step S5, third flow rate adjustment device 19 to be set in the open state, transitions to a normal control state for cooling operation, and makes a return.

When cooling operation is started, second flow rate adjustment device 18 and third flow rate adjustment device 19 are controlled in this way, and accordingly advantageous effects as described above can be obtained.

Second flow rate adjustment device 18 capable of blocking refrigerant from flowing into refrigerant storage device 16 is provided, and second flow rate adjustment device 18 is controlled to be set in the full-close state when cooling operation is started. Under such control, flow of refrigerant from the downstream side of first flow rate adjustment device 14 to refrigerant storage device 16 is blocked when cooling operation is started under the condition that the outdoor air temperature is extremely low. Accordingly, refrigerant can be prevented from flowing into refrigerant storage device 16 when cooling operation is started under the condition that the outdoor air temperature is extremely low. In this way, during cooling operation, shortage of the amount of refrigerant can be avoided and thus deterioration of the function of refrigeration cycle apparatus 1 can be avoided.

When discharge temperature T1 of compressor 13 is higher than a threshold value at the start of cooling operation, third flow rate adjustment device 19 is set in the open state, so that liquid refrigerant flows from first branch path F41 through first check valve 21 to third flow rate adjustment device 19, and further flows through third flow rate adjustment device 19 into supply path F43 and to the suction side of compressor 13. In this way, compressor 13 can be prevented from being superheated, even when refrigerant that is likely to be increased in temperature, like R32 refrigerant, for example, is used.

In refrigeration cycle apparatus 1, second flow rate adjustment device 18 is newly provided that enables control for blocking refrigerant from flowing into refrigerant storage device 16. As a flow rate adjustment device located in second refrigerant path F2 to reduce the pressure of refrigerant and thereby expand the refrigerant, conventionally a flow rate adjustment device for cooling operation and a flow rate adjustment device for heating operation are provided separately from each other. In contrast, in refrigeration cycle apparatus 1, a single first flow rate adjustment device 14 is provided that functions as both a flow rate adjustment device for cooling operation and a flow rate adjustment device for heating operation. Thus, the total number of flow rate adjustment devices in refrigeration cycle apparatus 1 does not increase. Even when second flow rate adjustment device 18 is newly provided, increase of the number of output ports required for controlling an actuator on the control circuit board of controller 100 can therefore be avoided.

In second refrigerant path F2 of refrigeration cycle apparatus 1, a single first flow rate adjustment device 14 is provided that serves as both a flow rate adjustment device for cooling operation and a flow rate adjustment device for heating operation, as a flow rate adjustment device that reduces the pressure of refrigerant to thereby expand the refrigerant. Therefore, in second refrigerant path F2, the path through which liquid refrigerant flows is different depending on whether cooling operation is performed or heating operation is performed. In second refrigerant flow path F2 of refrigeration cycle apparatus 1, first branch path F41 is provided between first flow rate adjustment device 14 and first heat exchanger 11 that is a part of the path through which liquid refrigerant flows during cooling operation, so that liquid refrigerant flows through first check valve 21 to third flow rate adjustment device 19. Further, in second refrigerant path F2 of refrigeration cycle apparatus 1, second branch path F42 is provided between first flow rate adjustment device 14 and second heat exchanger 12 that is a part of the path through which liquid refrigerant flows during heating operation, so that liquid refrigerant flows through second check valve 22 to third flow rate adjustment device 19. In this way, even when a single first flow rate adjustment device 14 serves as both a flow rate adjustment device for cooling operation and a flow rate adjustment device for heating operation, liquid refrigerant can always be supplied through third flow rate adjustment device 19 to compressor 13.

Embodiment 2

In connection with Embodiment 2, a description is given of an example where control of second flow rate adjustment device 18 is performed during defrosting operation for heating operation, in addition to control of second flow rate adjustment device 18 and third flow rate adjustment device 19 at the start of cooling operation as illustrated above in connection with Embodiment 1.

FIGS. 4 and 5 show a refrigerant circuit configuration of a refrigeration cycle apparatus 1A according to Embodiment 2. FIG. 4 shows a state of a refrigerant circuit in refrigeration cycle apparatus 1A during cooling operation. FIG. 5 shows a state of the refrigerant circuit in refrigeration cycle apparatus 1A during heating operation. In FIGS. 4 and 5 , the direction in which refrigerant flows is indicated by arrows.

For performing defrosting operation when a condition for starting the defrosting operation is satisfied during heating operation, it is necessary to discharge refrigerant stored in refrigerant storage device 16 during heating operation and use the refrigerant as refrigerant for defrosting operation in order to ensure a defrosting capability.

When defrosting operation is to be performed, if the temperature of refrigerant storage device 16 is a relatively high temperature, as in the case where heating operation is performed for a relatively long period of time immediately before the condition for starting the defrosting operation is satisfied, and if second flow rate adjustment device 18 is set in the full-open state, refrigerant in refrigerant storage device 16 is discharged through second flow rate adjustment device 18, since the pressure in refrigerant storage device 16 is higher than the pressure in second refrigerant path F2 between first flow rate adjustment device 14 and second heat exchanger 12. In contrast, when defrosting operation is to be performed, if the temperature of refrigerant storage device 16 is a relatively low temperature, as in the case where heating operation is performed for a short period of time immediately before the condition for starting the defrosting operation is satisfied, refrigerant in refrigerant storage device 16 may not be discharged through second flow rate adjustment device 18 even when second flow rate adjustment device 18 is set in the full-open state, since the pressure in refrigerant storage device 16 is lower than the pressure in second refrigerant path F2 between first flow rate adjustment device 14 and second heat exchanger 12.

In connection with Embodiment 2, a description is given of features and control of refrigeration cycle apparatus 1A that enables, when defrosting operation is to be performed, refrigerant stored in refrigerant storage device 16 to be discharged, even when the temperature of refrigerant storage device 16 is a relatively low temperature when the condition for starting defrosting operation is satisfied.

Referring to FIGS. 4 and 5 , refrigeration cycle apparatus 1A of Embodiment 2 differs from refrigeration cycle apparatus 1 of Embodiment 1 in the following respect. First flow rate adjustment device 14 in second refrigerant flow path F2 is located in parallel with refrigerant storage device 16 in third refrigerant flow path F3. Refrigerant storage device 16 is equipped with a level sensor 61 that detects level L1 of the liquid surface of stored refrigerant. A detection signal of level sensor 61 is input to controller 100.

More specifically, first flow rate adjustment device 14 in second refrigerant path F2 is disposed at a position located in parallel with refrigerant storage device 16 in third refrigerant path F3, and located between first branch path F41 and second branch path F42. Accordingly, during heating operation, second refrigerant path F2 between first flow rate adjustment device 14 and first heat exchanger 11 is in the low-temperature low-pressure state.

First flow rate adjustment device 14 is disposed at such a position, and therefore, third check valve 17 is disposed in such a manner that enables refrigerant to be discharged in only the one direction from the inside of refrigerant storage device 16 to the second refrigerant path between first heat exchanger 11 and first flow rate adjustment device 14. Third check valve 17 causes refrigerant to be discharged from the inside of refrigerant storage device 16 in only the one direction to the second refrigerant path between first heat exchanger 11 and first flow rate adjustment device 14, when the pressure in refrigerant storage device 16 is higher, by a reference value or more, than the pressure of second refrigerant path F2 between first heat exchanger 11 and first flow rate adjustment device 14.

Such refrigeration cycle apparatus 1A operates similarly to refrigeration cycle apparatus 1 according to Embodiment 1, except for defrosting operation.

FIG. 6 is a flowchart of control for CPU 102 of controller 100 to perform defrosting operation during heating operation, according to Embodiment 2.

In step S11, controller 100 determines whether or not the condition for starting defrosting operation as described above is satisfied, after heating operation is started. When controller 100 determines in step S11 that the condition for starting defrosting operation is not satisfied, controller 100 makes a return. When controller 100 determines in step S11 that the condition for starting defrosting operation is satisfied, controller 100 proceeds to step S12 to determine whether or not the operating time for which immediately preceding heating operation is performed is a long time more than or equal to a threshold value. The operating time for which immediately preceding heating operation is performed refers to the duration of the heating operation that has been performed immediately before the condition for starting defrosting operation is satisfied. The duration of the heating operation is obtained by controller 100 measuring the duration of the operation. The threshold value is set to a duration of heating operation that causes refrigerant stored in refrigerant storage device 16 during heating operation to reach a reference temperature or more that enables refrigerant stored in refrigerant storage device 16 during heating operation to be discharged easily through second flow rate adjustment device 18.

When controller 100 determines in step S12 that the operating time of the immediately preceding heating operation is a long time of more than or equal to a threshold value, controller 100 proceeds to step S13 to start defrosting operation, and proceeds to step S14 to set second flow rate adjustment device 18 in the full-open state. In this case, the operating time of the immediately preceding heating operation has caused refrigerant stored in refrigerant storage device 16 during heating operation to reach a reference temperature of more that enables the refrigerant to be discharged easily through second flow rate adjustment device 18. Therefore, refrigerant stored in refrigerant storage device 16 is discharged through second flow rate adjustment device 18 in the full-open state, because the pressure inside refrigerant storage device 16 is higher than the pressure in second refrigerant path F2 between second heat exchanger 12 and first flow rate adjustment device 14.

In step S15, controller 100 determines whether or not the liquid amount of refrigerant in refrigerant storage device 16 that is identified from level L1 of refrigerant detected by level sensor 61 is smaller than a threshold value. The threshold value is set to the amount from which it is recognized that the minimum amount of refrigerant required for defrosting operation has been discharged, from the amount of refrigerant stored in refrigerant storage device 16 during heating operation. Controller 100 waits until the liquid amount of refrigerant specified from detected level L1 of refrigerant becomes less than or equal to the threshold value in step S15. After this, defrosting operation is performed until the condition for starting defrosting operation is no more satisfied.

When controller 100 determines in step S12 that the operating time of the immediately preceding heating operation is not more than or equal to the threshold value, controller 100 controls, in step S16, second flow rate adjustment device 18 to reduce the opening of second flow rate adjustment device 18 to a reference opening, such that the pressure inside refrigerant storage device 16 becomes higher than the pressure of second refrigerant path F2 between second heat exchanger 12 and first flow rate adjustment device 14. In this case, refrigerant stored in refrigerant storage device 16 during heating operation has not reached the reference temperature or more that enables refrigerant stored in refrigerant storage device 16 during heating operation to be discharged easily through second flow rate adjustment device 18, as a result of the operating time of the immediately preceding heating operation, while second refrigerant path F2 between second heat exchanger 12 and first flow rate adjustment device 14 during heating operation is in the low-pressure state. Thus, when the control in step S16 causes the pressure inside refrigerant storage device 16 to become higher, by a reference value or more, than the pressure of second refrigerant path F2 between first heat exchanger 11 and first flow rate adjustment device 14, refrigerant is discharged from the inside of refrigerant storage device 16 through third check valve 17 into the second refrigerant path between first heat exchanger 11 and first flow rate adjustment device 14.

Then, controller 100 determines in step S17 whether or not the liquid amount of refrigerant specified from level L1 of refrigerant in refrigerant storage device 16 which is detected by level sensor 61, is less than or equal to a threshold value. The threshold value is the same as the threshold value used in step S15. Controller 100 waits until the liquid amount of refrigerant identified from the detected refrigerant level L1 becomes less than or equal to the threshold value in step S17, then causes defrosting operation to be started, and makes a return. After this, the defrosting operation is performed until the condition for starting the defrosting operation is no more satisfied.

As described above, when defrosting operation is started in Embodiment 2, controller 100 controls second flow rate adjustment device 18 such that refrigerant is discharged until the liquid amount of refrigerant stored in refrigerant storage device 16 becomes less than or equal to the threshold value. In this way, the defrosting capability during defrosting operation can be ensured regardless of the state of refrigerant storage device 16. In Embodiment 2, it is determined whether or not the liquid amount of refrigerant, which is identified from level L1 of refrigerant in refrigerant storage device 16 detected by level sensor 61, is less than or equal to the threshold value, and thus it is determined whether or not the liquid amount of refrigerant stored in refrigerant storage device 16 is less than or equal to the threshold value, and therefore, the fact that the liquid amount of refrigerant stored in refrigerant storage device 16 has become less than or equal to the threshold value can easily be confirmed.

Whether to perform control to set second flow rate adjustment device 18 in the full-open state in step S14 or perform control to reduce the opening of second flow rate adjustment device 18 to a reference opening in step S16, may be determined in the following manner. For example, when heating operation has been performed immediately before defrosting operation is started, refrigerant storage device 16 may be recognized as having been heated and control may be performed to set second flow rate adjustment device 18 in the full-open state. In contrast, when heating operation has not been performed immediately before defrosting operation is started but stopped before defrosting operation is started, refrigerant storage device 16 may be recognized as not having been heated and control may be performed to reduce the opening of second flow rate adjustment device 18 to a reference opening.

Alternatively, whether to perform control to set second flow rate adjustment device 18 in the full-open state in step S14 or perform control to reduce the opening of second flow rate adjustment device 18 to a reference opening in step S16, may be determined in the following manner. For example, refrigerant storage device 16 may be equipped with a temperature sensor and, when the temperature of refrigerant storage device 16 detected by this temperature sensor is higher than or equal to a threshold value that is the temperature regarded as causing refrigerant stored in refrigerant storage device 16 to be discharged through second flow rate adjustment device 18, control may be performed to set second flow rate adjustment device 18 in the full-open state and, when the temperature of refrigerant storage device 16 detected by the temperature sensor is lower than the threshold value, control may be performed to reduce the opening of second flow rate adjustment device 18 to a reference opening.

The liquid amount of refrigerant stored in refrigerant storage device 16 that is determined in steps S15 and S17 may also be determined based on the degree of subcooling on the outlet side of second heat exchanger 12 during heating operation. The liquid amount of refrigerant stored in refrigerant storage device 16 that is determined in steps S15 and S17 may also be determined based on the degree of subcooling on the outlet side of first heat exchanger 11 during defrosting operation.

Embodiment 3

In connection with Embodiment 3, a description is given of a modification of the control of second flow rate adjustment device 18 during defrosting operation in heating operation illustrated in connection with Embodiment 2.

FIG. 7 is a flowchart of control for CPU 102 of controller 100 to perform defrosting operation during heating operation, according to Embodiment 3. The control in FIG. 7 differs from the control in FIG. 6 in that the former performs step S17A instead of step S17 in FIG. 6 .

After reducing the opening of second flow rate adjustment device 18 to a reference opening in step S16, controller 100 determines in step S17A whether or not a reference time has elapsed since the reduction of the opening of second flow rate adjustment device 18 to the reference opening. The reference time in step S17A is set to the time determined at the time of design that causes the minimum amount of refrigerant required for defrosting operation to be discharged from refrigerant storage device 16 through third check valve 17. The reference time in step S17A is measured, in controller 100, with a timer that starts measuring the time when the opening of second flow rate adjustment device 18 is reduced to the reference opening in step S16.

The reference time in step S17A may be set based on a correlation between a pressure difference between the pressure in third refrigerant path F3 on the second heat exchanger 12-side of second flow rate adjustment device 18 and the pressure in third refrigerant path F3 on the outlet side of third check valve 17, when the opening of second flow rate adjustment device 18 is reduced to the reference opening in step S16, and the time taken by the minimum amount of refrigerant required for defrosting operation to be discharged from refrigerant storage device 16 through third check valve 17. This is for the reason that the larger the aforementioned pressure difference, the shorter the time taken by the minimum amount of refrigerant required for defrosting operation to be discharged.

For example, a data table is stored in memory 104 that is used for determining the aforementioned reference time from the aforementioned pressure difference based on the aforementioned correlation. A pressure sensor that detects the pressure in third refrigerant path F3 on the second heat exchanger 12-side of second flow rate adjustment device 18, and a pressure sensor that detects the pressure in third refrigerant path F3 on the outlet side of third check valve 17 are provided. When the opening of second flow rate adjustment device 18 is reduced to the reference opening in step S16, controller 100 calculates, based on respective pressures detected by these pressure sensors, the pressure difference between the pressure in third refrigerant path F3 on the second heat exchanger 12-side of second flow rate adjustment device 18 and the pressure in third refrigerant path F3 on the outlet side of third check valve 17. Based on the pressure difference thus calculated, controller 100 uses the data table stored in memory 104 to determine the reference time and determine whether or not the reference time has elapsed in step S17A.

As described above, in Embodiment 3, controller 100 controls, when starting defrosting operation, second flow rate adjustment device 18 in such a manner that refrigerant stored in refrigerant storage device 16 is discharged until the liquid amount of the refrigerant stored in refrigerant storage device 16 becomes less than or equal to a threshold value. Thus, regardless of the state of refrigerant storage device 16, the defrosting capability during defrosting operation can be ensured. In Embodiment 3, it is determined whether or not the liquid amount of refrigerant stored in refrigerant storage device 16 has become less than or equal to the threshold value, by checking the time elapsed from the reduction of the opening of second flow rate adjustment device 18 to the reference opening, and therefore, it can be determined easily that the liquid amount of refrigerant stored in refrigerant storage device 16 has become less than or equal to the threshold value.

In Embodiments 1 to 3 described above, there is a possibility that the passage between first check valve 21 and third flow rate adjustment device 19 and the passage between second check valve 22 and third flow rate adjustment device 19 are filled with liquid, when third flow rate adjustment device 19 fails, and therefore, these passages may be equipped with a pressure relief valve to discharge refrigerant through the pressure relief valve and thereby reduce the pressure. The pressure of these passages may also be reduced through rupture of a rupture plate provided in these passages.

SUMMARY OF EMBODIMENTS

The above-described embodiments are described again with reference to the drawings.

The preset disclosure relates to refrigeration cycle apparatus 1, 1A. Refrigeration cycle apparatus 1, 1A includes: compressor 13 provided in first refrigerant path F1 located between first heat exchanger 11 and second heat exchanger 12; first flow rate adjustment device 14 provided in second refrigerant path F2 located between first heat exchanger 11 and second heat exchanger 12; refrigerant storage device 16 provided in third refrigerant path F3 located between first heat exchanger 11 and second heat exchanger 12, third refrigerant path F3 being connected in parallel with a part of second refrigerant path F2, refrigerant storage device 16 being configured to store refrigerant flowing from second refrigerant path F2; second flow rate adjustment device 18 provided in third refrigerant path F3, and configured to adjust a flow rate of refrigerant between refrigerant storage device 16 and second refrigerant path F2; and controller 100 configured to control, when cooling operation is started, second flow rate adjustment device 18 to block flow of refrigerant from second refrigerant path F2 into refrigerant storage device 16.

As a result of these features, second flow rate adjustment device 18 is controlled, when cooling operation is started, to block flow of refrigerant from second refrigerant path F2 into refrigerant storage device 16, and therefore, when cooling operation is started under the condition that the outdoor air temperature is extremely low, refrigerant can be prevented from flowing into refrigerant storage device 16. Thus, in the refrigeration cycle apparatus of the present disclosure, there is no shortage of the amount of refrigerant for cooling operation, and deterioration of the function of the refrigeration cycle apparatus can be avoided.

Preferably, first flow rate adjustment device 14 is controlled by controller 100 to adjust a flow rate of refrigerant for both cooling operation and heating operation. As a result of these features, first flow rate adjustment device 14 adjusts the flow rate of refrigerant for both cooling operation and heating operation, and therefore, even when second flow rate adjustment device 18 is newly provided to block flow of refrigerant from second refrigerant path F2 into refrigerant storage device 16, increase of the number of output ports necessary for controlling an actuator on the control circuit board of controller 100 can be avoided.

More preferably, the refrigeration cycle apparatus further includes: third flow rate adjustment device 19 provided in a fourth refrigerant path located between second refrigerant path F2 and a suction side of compressor 13, the third flow rate adjustment device being configured to supply liquid refrigerant to compressor 13; first branch path F41 that branches off from a path between the first heat exchanger and first flow rate adjustment device 14 in second refrigerant path F2, and is connected to an inlet side of third flow rate adjustment device 19; second branch path F42 that branches off from a path between the second heat exchanger and first flow rate adjustment device 14 in second refrigerant path F2, and is connected to the inlet side of third flow rate adjustment device 19; first check valve 21 located in first branch path F41 and configured to supply the liquid refrigerant in a single direction to the inlet side of third flow rate adjustment device 19; and second check valve 22 located in second branch path F42 and configured to supply the liquid refrigerant in a single direction to the inlet side of third flow rate adjustment device 19. As a result of these features, liquid refrigerant in second refrigerant path F2 flows, during cooling operation, from first branch path F41 through first check valve 21 to third flow rate adjustment device 19 and, during heating operation, liquid refrigerant flows from second branch path F42 through second check valve 22 to third flow rate adjustment device 19, and therefore, even when a single first flow rate adjustment device 14 functions as both the flow rate adjustment device for cooling operation and the flow rate adjustment device for heating operation, liquid refrigerant can always be supplied through third flow rate adjustment device 19 to compressor 13.

More preferably, the refrigeration cycle apparatus further includes discharge temperature sensor 51 configured to detect a temperature on a discharge side of compressor 13, controller 100 controls third flow rate adjustment device 19 to be in an open state, when the temperature on the discharge side of compressor 13 detected by discharge temperature sensor 51 exceeds a threshold value. As a result of these features, even when refrigerant that is likely to be increased in temperature, such as R32 refrigerant for example, is used, compressor 13 can be prevented from being superheated.

More preferably, first flow rate adjustment device 14 is located, in second refrigerant path F2, in parallel with refrigerant storage device 16, the refrigeration cycle apparatus further includes a third check valve provided in third refrigerant path F3 and is configured to discharge refrigerant in refrigerant storage device 16 in a single direction to second refrigerant path F2 located between the first heat exchanger and first flow rate adjustment device 14, and when starting defrosting operation, controller 100 controls second flow rate adjustment device 18 to discharge refrigerant in refrigerant storage device 16 until an amount of refrigerant stored in refrigerant storage device 16 becomes less than or equal to a threshold value. As a result of these features, the defrosting capability during defrosting operation can be ensured regardless of the state of refrigerant storage device 16.

More preferably, the refrigeration cycle apparatus further includes a storage amount detection sensor configured to detect an amount of refrigerant stored in refrigerant storage device 16 and, when starting the defrosting operation, controller 100 controls, based on the amount of stored refrigerant detected by the storage amount detection sensor, second flow rate adjustment device 18 to discharge refrigerant in refrigerant storage device 16 through second flow rate adjustment device 18 until the amount of refrigerant stored in refrigerant storage device 16 becomes less than or equal to a threshold value. As a result of these features, refrigerant stored in refrigerant storage device 16 can be discharged while refrigerant storage device 16 has a relatively high temperature.

More preferably, the refrigeration cycle apparatus further includes a storage amount detection sensor configured to detect an amount of refrigerant stored in refrigerant storage device 16 and, when starting the defrosting operation, controller 100 controls, based on the amount of stored refrigerant detected by the storage amount detection sensor, second flow rate adjustment device 18 to discharge refrigerant in refrigerant storage device 16 through the third check valve until the amount of refrigerant stored in refrigerant storage device 16 becomes less than or equal to a threshold value. As a result of these features, refrigerant stored in refrigerant storage device 16 can be discharged while refrigerant storage device 16 has a relatively low temperature.

More preferably, when starting the defrosting operation, controller 100 controls second flow rate adjustment device 18 to discharge refrigerant in refrigerant storage device 16 through third check valve 17 for a predetermined time until the amount of refrigerant stored in refrigerant storage device 16 becomes less than or equal to a threshold value. Thus, it is easy to confirm that the amount of liquid refrigerant stored in refrigerant storage device 16 becomes less than or equal to a threshold value.

As described above, in refrigeration cycle apparatus 1 of Embodiment 1, refrigeration cycle apparatus 1A of Embodiment 2, and refrigeration cycle apparatus 1A of Embodiment 3, second flow rate adjustment device 18 is controlled, when cooling operation is started, to block flow of refrigerant from second refrigerant path F2 into refrigerant storage device 16, and therefore, when cooling operation is started under the condition that the outdoor air temperature is extremely low, refrigerant can be prevented from flowing into refrigerant storage device 16. Thus, in the refrigeration cycle apparatus of the present disclosure, there is no shortage of the amount of refrigerant for cooling operation, and deterioration of the function of the refrigeration cycle apparatus can be avoided.

It should be construed that the embodiments disclosed herein are given by way of illustration in all respects, not by way of limitation. It is intended that the scope of the present disclosure is defined by claims, not by the above description of the embodiments, and encompasses all modifications and variations equivalent in meaning and scope to the claims. 

1. A refrigeration cycle apparatus comprising: a first heat exchanger; a second heat exchanger; a compressor provided in a first refrigerant path located between the first heat exchanger and the second heat exchanger; a first flow rate adjustment device provided in a second refrigerant path located between the first heat exchanger and the second heat exchanger; a refrigerant storage device provided in a third refrigerant path located between the first heat exchanger and the second heat exchanger, the third refrigerant path being connected in parallel with a part of the second refrigerant path, the refrigerant storage device being configured to store refrigerant flowing from the second refrigerant path; a second flow rate adjustment device provided in the third refrigerant path and located between the refrigerant storage device and the second heat exchanger, the second flow rate adjustment device being configured to adjust a flow rate of refrigerant between the refrigerant storage device and the second refrigerant path located between the second heat exchanger and the first flow rate adjustment device; and a controller configured to control, when cooling operation is started, the second flow rate adjustment device to block flow of refrigerant from the second refrigerant path into the refrigerant storage device.
 2. The refrigeration cycle apparatus according to claim 1, wherein the first flow rate adjustment device is controlled by the controller to adjust a flow rate of refrigerant for both cooling operation and heating operation.
 3. The refrigeration cycle apparatus according to claim 2, further comprising: a third flow rate adjustment device provided in a fourth refrigerant path located between the second refrigerant path and a suction side of the compressor, the third flow rate adjustment device being configured to supply liquid refrigerant to the compressor; a first branch path that branches off from a path between the first heat exchanger and the first flow rate adjustment device in the second refrigerant path, and is connected to an inlet side of the third flow rate adjustment device; a second branch path that branches off from a path between the second heat exchanger and the first flow rate adjustment device in the second refrigerant path, and is connected to the inlet side of the third flow rate adjustment device; a first check valve located in the first branch path and configured to supply the liquid refrigerant in a single direction to the inlet side of the third flow rate adjustment device; and a second check valve located in the second branch path and configured to supply the liquid refrigerant in a single direction to the inlet side of the third flow rate adjustment device.
 4. The refrigeration cycle apparatus according to claim 3, further comprising a temperature sensor configured to detect a temperature on a discharge side of the compressor, wherein the controller controls the third flow rate adjustment device to be in an open state, when the temperature on the discharge side of the compressor detected by the temperature sensor exceeds a threshold value.
 5. The refrigeration cycle apparatus according to claim 1, wherein the first flow rate adjustment device is located, in the second refrigerant path, in parallel with the refrigerant storage device, the refrigeration cycle apparatus further comprises a third check valve provided in the third refrigerant path and is configured to discharge refrigerant in the refrigerant storage device in a single direction to the second refrigerant path located between the first heat exchanger and the first flow rate adjustment device, and when starting defrosting operation, the controller controls the second flow rate adjustment device to discharge refrigerant in the refrigerant storage device until an amount of refrigerant stored in the refrigerant storage device becomes less than or equal to a threshold value.
 6. The refrigeration cycle apparatus according to claim 5, further comprising a storage amount detection sensor configured to detect an amount of refrigerant stored in the refrigerant storage device, wherein when starting the defrosting operation, the controller controls, based on the amount of stored refrigerant detected by the storage amount detection sensor, the second flow rate adjustment device to discharge refrigerant in the refrigerant storage device through the second flow rate adjustment device until the amount of refrigerant stored in the refrigerant storage device becomes less than or equal to a threshold value.
 7. The refrigeration cycle apparatus according to claim 5, further comprising a storage amount detection sensor configured to detect an amount of refrigerant stored in the refrigerant storage device, wherein when starting the defrosting operation, the controller controls, based on the amount of stored refrigerant detected by the storage amount detection sensor, the second flow rate adjustment device to discharge refrigerant in the refrigerant storage device through the third check valve until the amount of refrigerant stored in the refrigerant storage device becomes less than or equal to a threshold value.
 8. The refrigeration cycle apparatus according to claim 5, wherein when starting the defrosting operation, the controller controls the second flow rate adjustment device to discharge refrigerant in the refrigerant storage device through the third check valve for a predetermined time until the amount of refrigerant stored in the refrigerant storage device becomes less than or equal to a threshold value. 